1. Technical Field of the Invention
The present invention relates generally to the fields of semiconductor lithography. More particularly, it concerns methods, compositions, and apparatuses relating to 157 nm and 193 nm soft pellicles.
2. Description of Related Art
In the production of semiconductor devices there are a number of lithographic exposure steps whereby an image is projected onto a photosensitive material coating on a semiconductor wafer. The image is projected using a photomask which must be kept clean because any undesired particles on the surface may alter the image on the wafer and cause a defect.
A common method to achieve this goal has been the application of a protective membrane, which is separated by a few millimeters from the mask itself. At this offset, particles on the protective membrane will be out of focus and not imaged onto the wafer. This membrane, called a “pellicle,” has been an integral part of the common practice in the semiconductor industry for two decades. The pellicle typically comprises a polymer membrane approximately one micrometer thick that is stretched over a frame which is affixed to a mask, also referred to as a “reticle.” Although the pellicle is in the optical path, the polymer thickness is small so that effect on the imaging performance is negligible.
Currently, there is no mask protection solution available for 157 nm lithography. The expectation is that any solution will be expensive and would likely add difficulty to the lithography process. The creation of a soft pellicle solution for 157 nm lithography would provide immense benefit to semiconductor manufactures by improving the yields and reducing the cost of 157 nm lithography.
Additionally, there are limited choices for 193 nm pellicles, raising the cost of the lithography. Improvements in 193 nm pellicles would provide benefit for semiconductor manufactures by reducing the costs of 193 nm lithography. All semiconductor manufactures and tool suppliers in the semiconductor industry would prefer a soft pellicle solution over a hard pellicle solution.